The present invention relates to an exposure apparatus used in a semiconductor manufacturing process, particularly, to a projection exposure apparatus which projects and transfers a reticle pattern onto a silicon wafer and, more particularly, to an exposure apparatus using a reticle stage and a wafer stage, which sequentially move a reticle and a silicon wafer with respect to a projection exposure system when projecting a reticle pattern onto the wafer.
A conventional semiconductor manufacturing process uses a projection exposure apparatus which projects and transfers a reticle pattern onto a silicon wafer.
A conventional projection exposure apparatus is shown in FIGS. 16 to 20.
In FIGS. 16 to 20, reference numeral 101 denotes an illumination system unit having an exposure light source and a function of shaping exposure light and irradiating a reticle with the shaped light; 102, a reticle stage which supports a reticle serving as an exposure pattern master and performs a reticle scan operation with respect to a wafer at a predetermined reduction exposure magnification ratio; 103, a reduction projection lens which reduces a master pattern and projects it onto a wafer (substrate); 104, a wafer stage which sequentially, continuously moves a substrate (wafer) for every exposure; and 105, an exposure apparatus main body which supports the reticle stage 102, reduction projection lens 103, and wafer stage 104.
Reference numerals 106 and 107 denote a wafer stage purge partition and a reticle stage space purge partition for purging the wafer and reticle stage spaces with helium or nitrogen. The purposes of these partitions are to prevent, in general air, ozone generated by absorbing, in oxygen in air, F2 laser (xcex=157 nm), which is vacuum ultraviolet radiation (VUV) serving as exposure light, to prevent silicon oxide generated by absorption in silicon in air, and to prevent a decrease in the transmittance of exposure light caused by ammonia or silanol, which is generated by hydrolysis of organic gas such as siloxane or silazane and moisture in the air, and attaches to lens glass.
In other words, the wafer stage space is closed for efficient purge with helium or nitrogen supplied to increase the transmittance of exposure light. The oxygen and moisture concentrations in the space are decreased to 100 to 1,000 ppm.
Reference numeral 108 denotes a wafer purge nozzle, which is arranged to locally purge an exposure portion on the upper surface of a wafer with high-purity nitrogen gas and decreases oxygen and moisture concentrations to 10 ppm or less, which is lower than the oxygen concentrations (100 to 1,000 ppm) within the wafer stage purge partition 106 and reticle stage purge partition 107.
A wafer stage purge pipe 109, reticle stage purge pipe 110, and wafer purge pipe 111 are used to supply purge gas (helium, nitrogen, or the like) from a purge gas supply unit 112, to interiors of the partitions and the purge nozzle.
In FIG. 17, reference numeral 115 denotes a wafer whose single-crystal silicon substrate surface is coated with a resist in order to project and to transfer a reticle pattern drawn on a reticle substrate via a reduction exposure system; 113, a fine moving stage, which finely adjusts the wafer 115 in the optical axis direction and tilt direction of the reduction exposure system and a rotational direction of the reduction exposure system and a rotational direction about the optical axis as a center; 114, a wafer chuck, which supports and fixes the wafer 115 onto the fine moving stage 113; 116, an X bar mirror, which is a target for measuring the X position of the fine moving stage 113 by a laser interferometer; 117, a Y bar mirror, which is a target for measuring the Y position of the fine moving stage 113, and 118, an illuminance sensor, which is arranged on the upper surface of the fine moving stage 113, calibrates and measures the illuminance of exposure light before exposure, and uses the illuminance for correction of the exposure amount.
Reference numeral 119 denotes a stage reference mark, which is arranged on the upper surface of the fine moving stage 113 and has a stage alignment measurement target; 120, an X linear motor, which moves and drives the fine moving stage 113 in the X direction; 121, an X guide, which moves and guides the fine moving stage 113 in the X direction; 122, a Y guide, which moves and guides the X guide 121 and fine moving stage 113 in the Y direction; 123 and 124, Y linear motors, which move and drive the fine moving stage 113 in the Y direction; and 125, a stage surface plate, which plane-guides the fine moving stage 113.
As shown in FIGS. 18A and 18B, slit exposure light 126 is emitted to the center of the optical path of the exposure light. The wafer purge nozzle 108 is set above the exposed portion, and the space above the wafer 115 is purged with purge gas (nitrogen or the like) injected from the wafer purge nozzle 108. An oxygen concentration of 10 ppm is achieved around the center of the wafer 115. As shown in FIGS. 19A, 19B, 20A, and 20B, a gap of up to about 1 mm is formed between the wafer purge nozzle 108 and the wafer 115 in the direction of height, and a gap of up to about 2 mm is formed between the wafer purge nozzle 108 and the wafer chuck 114 when a shot near the periphery of the wafer 115 is to be exposed with the slit exposure light 126. The conventional wafer chuck 114 does not have a peripheral member which shields the wafer chuck 114 from a purge gas flow from the wafer purge nozzle 108. In exposing the wafer periphery, purge gas from the wafer purge nozzle 108 leaks in a large amount from the periphery of the wafer chuck 114 to decrease the pressure of the purge space. Gas other than purge gas externally flows into the purge space to increase the oxygen concentration to about 100 to 1,000 ppm. A low oxygen concentration equal to or less than a specified value (10 ppm or less) cannot be maintained.
The present invention has been made to overcome the conventional drawbacks, and has as its object to prevent a decrease in purge pressure in exposure and an increase in oxygen concentration caused by a purge error near the periphery of a wafer or a reticle.
To overcome the conventional drawbacks and to achieve the same object, an exposure apparatus according to the first aspect of the present invention has the following arrangement.
That is, the exposure apparatus comprises a movable stage, a chuck device, which is arranged on the stage and holds a substrate, a gas supply device for supplying gas to a position of the substrate to be exposed, and a planar member, which is arranged adjacent to a periphery of the substrate, is flush with or substantially flush with a surface of the substrate, and is integrated with the chuck device.
A device manufacturing method according to the present invention has the following steps.
That is, the device manufacturing method comprises the steps of applying a photosensitive material to a substrate, transferring a pattern to the photosensitive material applied to the substrate by the above-described exposure apparatus, and developing the substrate bearing the pattern.
Other objects and advantages besides those discussed above shall be apparent to those skilled in the art from the description of a preferred embodiment of the invention which follows. In the description, reference is made to the accompanying drawings, which form a part hereof, and which illustrate an example of the invention. Such an example, however, is not exhaustive of the various embodiments of the invention, and, therefore, reference is made to the claims which follow the description for determining the scope of the invention.